Secure Socket Layer is networking protocol used at transport layer to provide secure connection between client and server over internet. It places itself as and application layer protocol in the TCP/IP reference model and as presentation layer protocol in the OSI model.

A protocol data unit (PDU) is a single unit of information transmitted among peer entities of a computer network.
A PDU is composed of protocol specific control information and user data
Protocol data units for the Internet protocol suite are:
The transport layer PDU is the TCP segment for
→TCP, and the datagram for UDP.
→The Internet layer PDU is the packet.
→The link layer PDU is the frame.

(a) FALSE:
AMPS is a first-generation cellular technology that uses separate frequencies, or "channels", for each conversation (see frequency-division multiple access (FDMA)). It therefore required considerable bandwidth for a large number of users. In general terms, AMPS was very similar to the older "0G" Improved Mobile Telephone Service, but used considerably more computing power in order to select frequencies, hand off conversations to PSTN lines, and handle billing and call setup.
(b) TRUE:
IS - 95 is a second generation cellular phone system based on CDMA and DSSS.
(c) TRUE:
The Third generation cellular phone system will provide universal personnel communication.

→ The session layer is the network dialog controller. It establishes, maintains, and synchronizes the interaction among communicating systems.
→ Dialog control: The session layer allows two systems to enter into a dialog. It allows the communication between two processes to take place in either half-duplex (one way at a time) or full-duplex (two ways at a time) mode.
→ Synchronization: The session layer allows a process to add checkpoints, or synchronization points, to a stream of data. For example, if a system is sending a file of 2000 pages, it is advisable to insert checkpoints after every 100 pages to ensure that each 100-page unit is received and acknowledged independently. In this case, if a crash happens during the transmission of page 523, the only pages that need to be reset after system recovery are pages 501 to 523. Pages previous to 501 need not be resent.

● A repeater is an electronic device that receives a ​ signal​ and retransmits it.
● Repeaters are used to extend transmissions so that the signal can cover longer distances or be received on the other side of an obstruction.
● Physical layer in the OSI model plays the role of interacting with actual hardware and signaling mechanism

1. Repeater→ Physical layer: Its job is to regenerate the signal over the same network before the signal becomes too weak or corrupted so as to extend the length to which the signal can be transmitted over the same network.
2. Gateway→ All seven layers: A gateway, as the name suggests, is a passage to connect two networks together that may work upon different networking models. They basically works as the messenger agents that take data from one system, interpret it, and transfer it to another system. Gateways are also called protocol converters and can operate at any network layer. Gateways are generally more complex than switch or router.
3. Router→ Network layer: A router is a device like a switch that routes data packets based on their IP addresses. Router is mainly a Network Layer device. Routers normally connect LANs and WANs together and have a dynamically updating routing table based on which they make decisions on routing the data packets. Router divide broadcast domains of hosts connected through it.
Bridge→ Data link layer: A bridge is a repeater, with add on functionality of filtering content by reading the MAC addresses of source and destination. It is also used for interconnecting two LANs working on the same protocol. It has a single input and single output port, thus making it a 2 port device.

●The term "bit stuffing" broadly refers to a technique whereby extra bits are added to a data stream, which do not themselves carry any information, but either assist in management of the communications or deal with other issues.
●The receiver knows how to detect and remove or disregard the stuffed bits.